The U.S. Environmental Protection Agency will take one of the biggest hits of any federal agency if the government shuts down this week, operating with under 7 percent of its employees, according to guidance issued by the agency.

Among those furloughed would be most workers at the Office of Air and Radiation, which is in charge of writing and implementing most of the EPA’s major air pollution rules. The clock would also stop, for now, on the EPA’s eagerly-awaited proposal on renewable fuel volume standards for 2014.

The EPA said its plan for dealing with a shutdown would classify 1,069 employees, out of 16,205, as essential. These employees would continue to work if Congress fails to secure a budget deal by midnight Monday to avoid disruption to federal funding.

Taking the air and radiation unit off the grid will tighten timelines to meet certain court-imposed deadlines, said one expert.

“People are not going to be able to be working on these rules at home,” said Dina Kruger, an environmental regulation consultant and former climate change director at the EPA, who worked at the agency when the government shut down in 1996.